LED Display Driver Circuit Brightness Non-Uniformity Correction
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Solution Overview
Problem
LED display driver circuits face non-uniformity issues at low brightness levels due to decreasing on-time, leading to undesirable brightness variance across LED display devices with high dynamic range and high resolution.
Innovation Solution
The implementation of a light-emitting diode (LED) display driver circuit with control circuitry that adjusts channel output currents using LED brightness estimates, obtained through current integration values, to equalize channel output currents and correct for brightness non-uniformity, employing test logic and external test circuitry to calculate and apply trim control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the on-time in each period is decreased to increase the number of LED pixels and decrease pitch, then the resolution and dynamic range of the LED display is improved, but the LED brightness uniformity deteriorates due to significant transient current portions and device/channel transient current variance
Solution Approach 1:
The patent applies preliminary action by measuring and storing individual LED brightness characteristics during a test phase before actual display operation. The control circuitry pre-calculates compensation values based on these measurements, so that when the display operates with reduced on-time, the compensation is already in place to counteract the transient current effects, thereby maintaining brightness uniformity despite the shortened duration
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the current waveform parameters (amplitude, duration, shape) for each LED channel based on its measured characteristics. The control circuitry modifies the drive parameters compensating for transient current variations, allowing the system to maintain brightness uniformity even when operating with reduced on-time periods required for high-resolution displays
2Manufacturing precision
If the number of RGB LED pixels is increased to achieve high resolution displays, then the display quality is improved, but the channel output current variance increases leading to brightness non-uniformity
Solution Approach 1:
The patent applies segmentation by dividing the LED display into individual controllable channels and treating each channel's transient current characteristics separately. The control circuitry measures and compensates for brightness variations on a per-channel basis, allowing high-resolution displays with many pixels to maintain uniformity by addressing each segment (channel) individually rather than treating the entire display as a uniform system
Solution Approach 2:
The patent implements feedback by measuring the actual brightness output of each LED channel and using this information to adjust the drive current accordingly. The control circuitry continuously monitors and compensates for channel-to-channel variations, creating a closed-loop system that maintains brightness uniformity across high-resolution displays with numerous channels despite inherent manufacturing variations
Data Source
AI summary
A light-emitting diode (LED) display driver circuit includes: a set of channels, each channel of the set of channels having a respective current control circuit; and control circuitry coupled to each respective current control circuit and configured to adjust a respective control signal to each respective current control circuit responsive to an LED brightness estimate for each channel of the set of channels.